Characterize, compare, and contrast the three types of papilloma virus isolated from cattle viz: bovine cutaneous papilloma virus (BCPV), the classical bovine papovirus; bovine alimentary papilloma virus (BAPV); and bovine udder papilloma virus (BUPV). Investigate alimentary squamous carcinomas found on bracken infested farms for the presence of papilloma virus genome. Make a similar study of the adenomas and adenocarcinomas found in the intestine. Set up experimental models in which the bracken fern component is replaced in "carcinogen plus virus" type experiments by such compounds as azothioprene to try to gain some insight into the nature of the mechanism of interplay of the dietary factor and the virus.